ssl.SSLError does NOT have 'reason' attribute. Use str() to get a
reliable string.

Fixed the silly bug in another CL: https://codereview.chromium.org/180273003/

The ssl.SSLError does NOT have attribute 'reason', and must use the
generic 'strerror' instead. This is what happens when I submit a CL
too fast...

BUG=346845
R=stip@chromium.org,maruel@chromium.org

Review URL: https://codereview.chromium.org/180723002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@253317 0039d316-1c4b-4281-b951-d872f2087c98